This invention relates to transparent acoustic barriers for use along highways, railroads and the like and to panel and joint assemblies useful in such barriers as well as in other constructions.
The need for acoustic barriers in urban environments to control highway, railway and rapid transit noise is well recognized. Barriers for this purpose of opaque construction are often objectionable because they block the view of travelers and in some instances are objectionable to residents of the affected urban area as well. Large sheets of transparent material such as safety glasses and synthetic resins, e.g., high strength polycarbonates, are in principle available for use in such impact-damage-prone barriers. However, not only is the cost of such materials great, but also the known systems for joining such panels to supporting structure raise numerous problems. For instance, it is difficult to secure the panels against hurricane force winds or other force conditions.
The support problems for panels for acoustic barriers as well as other applications is made worse for panels of synthetic materials due to the significant differences in the thermal expansion properties of synthetic panel materials and their metal supports. Channel supports that are constructed to accommodate panel movement during thermal expansion and contraction of the panel tend to increase the risk of withdrawal of the panels from their supports when the panels bow under wind or other loading. To stiffen the panels against bowing by increasing their thickness adds detrimentally to the cost of the panels. Similarly, to increase the size and complexity of the supports adds detrimentally to the cost. For reasons such as these, the use of synthetic panels has been limited.
A principal object of the invention is to overcome the various problems described.